Corrosion inhibiting butadiene styrene paint composition

ABSTRACT

COATING COMPOSITIONS, SUITABLE FOR PROVIDING ANTI-CORROSION COATINGS ON METAL SURFACES AND PARTICULARLY FOR APPLICATION TO RUSTY AND WEATHERED SURFACES COMPRISING A WATER BASED LATEX METAL PRIMER CONTAINING AN ADDITIVE MIXTURE OF DI-BASE AMMONIUM CITRATE AND A NEUTRALIZED ACIDIC PHOSPHATE CO-ESTER OF AN ALIPHATIC ALCOHOL AND A NON-IONIC ADDUCT OF ETHYLENE OXIDE AND AN ORGANIC COMPOUND CONTAINING REACTIVE HYDROGEN ATOMS.

United States Patent 3,586,519 CORROSION INHIBITING BUTADIENE STYRENEPAINT COMPOSITION John J. Hendricks, Flushing, N.Y., assignor to SapolinPaints, Inc., New York, N.Y. No Drawing. Filed June 6, 1969, Ser. No.831,222 Int. Cl. C09d /08 US. Cl. 106-14 2 Claims ABSTRACT OF THEDISCLOSURE Coating compositions, suitable for providing anti-corrosioncoatings on metal surfaces and particularly for application .to rustyand weathered surfaces comprising a water based latex metal primercontaining an additive mixture of di-basic ammonium citrate and aneutralized acidic phosphate co-ester of an aliphatic alcohol and anon-ionic adduct of ethylene oxide and an organic compound containingreactive hydrogen atoms.

This invention relates to improved coating compositions such as metalprimers Whose protective qualities render them highly satisfactory forimpeding and delaying the corrosion of metal surfaces and particularlyuseful in the recoating of rusted metal surfaces Without requiringextensive treatment of the rusted surface.

In the maintenance of metal structures exposed to the elements, thedevelopment of rust is a serious problem of long standing. Structuressuch as bridges, ship superstructures, storage tanks, chemical andrefinery plant structures, etc., have generally been protected bypainting and the protective coating must be renewed periodically.Usually, such metal structures, when first erected, are primed andtop-coated. After a period of exposure to the elements, the coatingweathers away and in areas where the coating is inadequate, rust forms.

Initial primers and primers used for recoating are formulated to givemaximum protection of the metal base against rusting. Generally, theavailable primers are more satisfactory for painting previouslyunpainted surfaces than they are recoating surfaces mainly because theunpainted metal is fairly smooth and free of rusty scale. Even thoseprimers specially formulated as recoating primers are known to failfirst in areas where such scaly, badly rusted areas are recoated. Oftenit is the practice to scrape off, sand blast, or otherwise remove asmuch rust as possible before recoating. Recoating of surfaces from whichrust has been removed usually gives satisfactory protection againstfurther rusting. It is impractical, however, to remove all rust fromlarge structures because of prohibitive costs. Accordingly, thestructure may be recoated with some rust still remaining. In such cases,primer/top-coat systems which will still afford good protection arerequired, but currently, the industry acknowledges that present primerswith few exceptions are lacking with respect to their adherence torusted areas. In all of the rust inhibitive aqueous priming systemswhich are commercially available and which the inventor is personallyfamiliar, the rust tends to bleed or migrate to the surface of theprimer whenever the rust has not been completely removed. However, withthe composition of the present invention, no bleeding or migration ofthe rust to the surface is evident with a coating in the order of 1.5mils dry film thickness.

Accordingly, in the usual practice it is necessary not only to removeall loose deposits from the surface to be recoated, but also to abradethe surface to remove mechanically the scale and the more firmlyadhering rust or other metal oxides.

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Thus, it is a principal object of this invention to eliminate theseprior art shortcomings, and, in accordance with this invention, it ispossible to apply directly to rusted metal surfaces a primer coatinghaving good bonding and adhesion characteristics; the only preliminarytreatment of the surface being the removal of scale.

In accordance with this invention, it has now been discovered that waterbase latex coating compositions having the ability to protect metalsurfaces against rusting and in particular the ability to coat badlyrusted metallic surfaces without extensive prior treatment of saidrusted areas may be prepared by the inclusion in the coating compositionof a new and novel mixture of di-basic ammonium citrate and thepotassium salt of a phosphate co-ester of aliphatic alcohol and anon-ionic adduct of ethylene oxide and organi compounds containingreactive hydrogen atoms. The acidic phosphate co-esters and theirneutralized derivates are more fully described in US. Pat. 3,380,927,issued Apr. 30, 1968, and the disclosure of this patent is hereinincorporated by reference. More specifically, the acidic phosphateco-esters are solubilized in polar media such as Water by neutralizationwith inorganic alkalis such as alkali metal hydroxides.

A preferred additive mixture for use in conferring desired properties tothe latex coating compositions of this invention is obtained by mixingdi-basic ammonium citrate with the potassium salt of a commerciallyavailable phosphate co-ester, i.e. the potassium salt of a complexorganic polyphosphoric ester acid known as Strodex PK-90, manufacturedby Dexter Chemical Corporation, Bronx, N.Y. The method of preparing thisphosphate coester is taught in the aforementioned Pat. 3,380,927.

In the preparation of the additive mixture, the neutralized phosphateco-esters and di-basic ammonium citrate are preferably mixed in equalproportions. However, the proportions of one component to the other maybe varied and effective results have been obtained by using either in aratio ranging from about 0.2:1 to 1:1.

In formulating the coating compositions of this invention, the combinedweight of the additives may comprise from 0.5 to 5% by weight of thecomposition.

In the experimentation leading to the novel additive mixture and coatingcomposition of this invention, Strodex PK90, described above, anddi-basic ammonium citrate were used separately in various water baselatex compositions. Neither material by itself was effective inproviding a satisfactory coating for rusted surfaces. The combinedeffect of the two components herein described, accordingly, isconsidered to be synergistic in nature.

It is generally known that most primers now in use exhibit a tendency tomerely cover the surface of a rusty area on ferrous and other metalswithout penetrating deeply thereinto. As a result, much porosity remainsin the rust layers. This porosity is very undesirable since rustingusually continues under the film. After a period of exposure to theelements, the coating film over the rust areas becomes blistered andthen flashes oif. It has now been found that the additive mixturehereinabove described, when incorporated in a primer coating, forexample markedly improves the wetting and penetrating properties of thecoating, while conferring other advantages such as improvedflexibilization of the resulting film and improved durability onexposure.

The following examples illustrate the merits of the additives of thisinvention in coatings for providing protective coating systems on clean(non-pre-rusted) and prerusted ferrous metal. While these examplesillustrate the best modes presently known for applying and practicingthe principles of this invention they are not intended to limit thisinvention in any sense.

3 EXAMPLE I A water based latex primer, typical of the compositionscoming within the scope of this invention was prepared by mixing thefollowing components:

Lbs.

Water 168 2% hydroxyethylcellulose solution 150 Strodex PK-90 3 28%ammonium hydroxide 4 Dibasic ammonium citrate 5 Basic silicate whitelead (80% PhD type) 100 Zinc oxide 50 Titanium dioxide 100 Bariumsulfate 200 Amorphous silica 50 Water soluble melamine 1 12 30% phenylmercuric acetate -5 Cobalt drier 4 Butadiene-styrene copolymer 375 1Cymel 301--Pr0duct of American Cyanamid Co.

Pliolite 491-P10duct of Goodrich Chemical Co.

In the formulation of the foregoing composition, the Strodex PK-9O andthe di-basic ammonium citrate were pre-mixed and then added to the latexcomposition.

Two steel panels, one clean (non-rusty) and one rusty, Were coated withthe foregoing formulation. Tests for salt spray resistance clearlyshowed that after one week there was no evidence of failure, that is,rusting on either panel.

EXAMPLE II A second formulation was prepared, using equivalentproportions of the same components, but omitting the Strodex PK-90 andthe di-basic ammonium citrate. Two steel panels, one clean (non-rusty)and one rusty, were coated with this formulation. Tests for salt sprayresistance clearly showed rust formation on both panels aftertwenty-four hours.

Similar tests were run with the formulation of Example II to which wereadded in one case, di-basic ammonium citrate and in another case,Strodex PK-90. Panels, rusted and unrusted, as in the foregoingexamples, were coated with these formulations and tested for salt sprayresistance. At the end of twenty-four hours, all panels coated withthese formulations showed rusted areas.

It is obvious that in the preparation of the novel compositions of thisinvention that modifications in formulations and variations inconcentrations may be made, as required. Obviously, these changes willbe dependent on the type of coating desired. It will be understood thatit is intended to cover all changes and modifications of the preferredembodiment of this invention, herein chosen for the purpose ofillustration, which do not constitute departures from the spirit andscope of the invention.

What is claimed is:

1. A corrosion inhibiting butadiene-styrene elastomeric paintcomposition consisting essentially of a butadienestyrene latex, di-basicammonium citrate and the potassium salt of a co-ester of (1) aphosphorous compound selected from the group consisting of phosphorouspentoxide, orthophosphoric acid and polyphosphoric acid, (2) analiphatic monohydric alcohol containing from 6 to 16 carbon atoms, and(3) a nonionic adduct of ethylene oxide and an organic compound selectedfrom the group consisting of alkylated phenols containing at least onealkyl group of 6 to 18 carbon atoms, aliphatic alcohols containing from6 to 25 carbon atoms, aliphatic monocarboxylic acids containing from 6to 20 carbon atoms, aliphatic amines containing 6 to 20 carbon atoms,and aliphatic mercaptans containing 6 to 20 carbon atoms, said nonionicadduct (3) containing from 1 to 40 mols of ethylene oxide per mol ofsaid organic compound, and being present in the weight proportions ofabout 5 to parts per parts combined of said nonionic adduct 3) and saidaliphatic monohydric alcohol (2), and the molar ratio of the totalnumber of mols combined of said aliphatic monohydric alcohol (2) and ofsaid nonionic adduct (3) to the total number of mols of said phosphorouscompound -(1), calculated as phosphorous pentoxide, being within therange from about 1:1 to about 5:1.

2. The composition of claim 1, wherein either component may be presentin a ratio of 0.2:1 to 1: 1.

References Cited UNITED STATES PATENTS 2,710,792 6/ 1955 McDonald et a1.25279.4X 3,162,547 12/1964 Kendall 25279.4X 3,380,927 4/1968 Edelsteinet a1. 252308 OTHER REFERENCES Rose and Rose: The Condensed ChemicalDictionary, 7th edition, Reinhold (1966), p. 57.

DONALD A. ARNOLD, Primary Examiner D. A. JACKSON, Assistant ExaminerU.S. C1. X.R. 25279.4, 308

